Forums

Jumper to replace Inductor

Started by rickman June 30, 2016
I want to use a linear regulator on a board where a buck switcher had 
been designed in.  No problem on the chip, there are thousands with a 
compatible footprint for this TSOP-5 package.  I need to replace the 
inductor with a jumper, something that can be SMT assembled and of 
course, inexpensive.

The pads are spaced so a 1206 would reach but it is a bit wide with the 
pads only 47 mils wide.  More importantly there are vias about 15 mils 
away which end up maybe 7 or 8 mils away with the wider part overhang. 
I'm a little concerned with this spacing.  An 0805 part would fit the 
pads better, but doesn't quite reach the gap of 82 mils.

I was searching for zero ohm resistors, but it occurred to me there may 
be parts specifically designed as jumpers which might fit these pads 
better.  Anyone know of anything like this?  Nearly any jumper of 110 to 
120 mils long and no more than 50 mils wide would do, better is 35 or 40 
mils wide.

I did find this which is a bit more than resistors at $450 per reel.

http://www.digikey.com/product-detail/en/harwin-inc/S1911-46R/952-1740-1-ND/3131071

If the assembly house doesn't like the 1206 resistor, it wouldn't be the 
worst thing...

-- 

Rick C
On 30/06/2016 16:26, rickman wrote:
> I want to use a linear regulator on a board where a buck switcher had > been designed in. No problem on the chip, there are thousands with a > compatible footprint for this TSOP-5 package. I need to replace the > inductor with a jumper, something that can be SMT assembled and of > course, inexpensive. > > The pads are spaced so a 1206 would reach but it is a bit wide with the > pads only 47 mils wide. More importantly there are vias about 15 mils > away which end up maybe 7 or 8 mils away with the wider part overhang. > I'm a little concerned with this spacing. An 0805 part would fit the > pads better, but doesn't quite reach the gap of 82 mils. > > I was searching for zero ohm resistors, but it occurred to me there may > be parts specifically designed as jumpers which might fit these pads > better. Anyone know of anything like this? Nearly any jumper of 110 to > 120 mils long and no more than 50 mils wide would do, better is 35 or 40 > mils wide. > > I did find this which is a bit more than resistors at $450 per reel. > > http://www.digikey.com/product-detail/en/harwin-inc/S1911-46R/952-1740-1-ND/3131071 > > > If the assembly house doesn't like the 1206 resistor, it wouldn't be the > worst thing...
1206 on its side? That'll confuse them. Cheers -- Syd
On Thu, 30 Jun 2016 11:26:41 -0400, rickman <gnuarm@gmail.com> Gave us:

>I want to use a linear regulator on a board where a buck switcher had >been designed in. No problem on the chip, there are thousands with a >compatible footprint for this TSOP-5 package. I need to replace the >inductor with a jumper, something that can be SMT assembled and of >course, inexpensive. > >The pads are spaced so a 1206 would reach but it is a bit wide with the >pads only 47 mils wide. More importantly there are vias about 15 mils >away which end up maybe 7 or 8 mils away with the wider part overhang. >I'm a little concerned with this spacing. An 0805 part would fit the >pads better, but doesn't quite reach the gap of 82 mils. > >I was searching for zero ohm resistors, but it occurred to me there may >be parts specifically designed as jumpers which might fit these pads >better. Anyone know of anything like this? Nearly any jumper of 110 to >120 mils long and no more than 50 mils wide would do, better is 35 or 40 >mils wide. > >I did find this which is a bit more than resistors at $450 per reel. > >http://www.digikey.com/product-detail/en/harwin-inc/S1911-46R/952-1740-1-ND/3131071 > >If the assembly house doesn't like the 1206 resistor, it wouldn't be the >worst thing...
A test point. Typically Silver Plated Copper or Tin plated Copper, but more often Silver as it takes solder better. http://www.digikey.com/product-detail/en/harwin-inc/S1751-46R/952-1478-2-ND/2264459
On Thu, 30 Jun 2016 14:27:53 -0400, DecadentLinuxUserNumeroUno
<DLU1@DecadentLinuxUser.org> Gave us:

>On Thu, 30 Jun 2016 11:26:41 -0400, rickman <gnuarm@gmail.com> Gave us: > >>I want to use a linear regulator on a board where a buck switcher had >>been designed in. No problem on the chip, there are thousands with a >>compatible footprint for this TSOP-5 package. I need to replace the >>inductor with a jumper, something that can be SMT assembled and of >>course, inexpensive. >> >>The pads are spaced so a 1206 would reach but it is a bit wide with the >>pads only 47 mils wide. More importantly there are vias about 15 mils >>away which end up maybe 7 or 8 mils away with the wider part overhang. >>I'm a little concerned with this spacing. An 0805 part would fit the >>pads better, but doesn't quite reach the gap of 82 mils. >> >>I was searching for zero ohm resistors, but it occurred to me there may >>be parts specifically designed as jumpers which might fit these pads >>better. Anyone know of anything like this? Nearly any jumper of 110 to >>120 mils long and no more than 50 mils wide would do, better is 35 or 40 >>mils wide. >> >>I did find this which is a bit more than resistors at $450 per reel. >> >>http://www.digikey.com/product-detail/en/harwin-inc/S1911-46R/952-1740-1-ND/3131071 >> >>If the assembly house doesn't like the 1206 resistor, it wouldn't be the >>worst thing... > > > A test point. Typically Silver Plated Copper or Tin plated Copper, >but more often Silver as it takes solder better. > >http://www.digikey.com/product-detail/en/harwin-inc/S1751-46R/952-1478-2-ND/2264459
So, you are ignoring the test point suggestion? Any time you need to replace a part already laid out with a jumper, you can use a test point. Two benefits... A: It is usually cheaper than a zero ohm resistor of the same form factor, and B: They are available of tape and reel and are pick and place compatible if you get the right type. Three if you count the fact that you can also actually use it as a test point.
On Thursday, 30 June 2016 16:26:43 UTC+1, rickman  wrote:
> I want to use a linear regulator on a board where a buck switcher had > been designed in. No problem on the chip, there are thousands with a > compatible footprint for this TSOP-5 package. I need to replace the > inductor with a jumper, something that can be SMT assembled and of > course, inexpensive. > > The pads are spaced so a 1206 would reach but it is a bit wide with the > pads only 47 mils wide. More importantly there are vias about 15 mils > away which end up maybe 7 or 8 mils away with the wider part overhang. > I'm a little concerned with this spacing. An 0805 part would fit the > pads better, but doesn't quite reach the gap of 82 mils. > > I was searching for zero ohm resistors, but it occurred to me there may > be parts specifically designed as jumpers which might fit these pads > better. Anyone know of anything like this? Nearly any jumper of 110 to > 120 mils long and no more than 50 mils wide would do, better is 35 or 40 > mils wide. > > I did find this which is a bit more than resistors at $450 per reel. > > http://www.digikey.com/product-detail/en/harwin-inc/S1911-46R/952-1740-1-ND/3131071 > > If the assembly house doesn't like the 1206 resistor, it wouldn't be the > worst thing...
Usually you can use a plain resistor ahead of a linear regulator, just pick whatever resistance won't cause problems anywhere. NT
On 6/30/2016 8:30 PM, tabbypurr@gmail.com wrote:
> On Thursday, 30 June 2016 16:26:43 UTC+1, rickman wrote: >> I want to use a linear regulator on a board where a buck switcher had >> been designed in. No problem on the chip, there are thousands with a >> compatible footprint for this TSOP-5 package. I need to replace the >> inductor with a jumper, something that can be SMT assembled and of >> course, inexpensive. >> >> The pads are spaced so a 1206 would reach but it is a bit wide with the >> pads only 47 mils wide. More importantly there are vias about 15 mils >> away which end up maybe 7 or 8 mils away with the wider part overhang. >> I'm a little concerned with this spacing. An 0805 part would fit the >> pads better, but doesn't quite reach the gap of 82 mils. >> >> I was searching for zero ohm resistors, but it occurred to me there may >> be parts specifically designed as jumpers which might fit these pads >> better. Anyone know of anything like this? Nearly any jumper of 110 to >> 120 mils long and no more than 50 mils wide would do, better is 35 or 40 >> mils wide. >> >> I did find this which is a bit more than resistors at $450 per reel. >> >> http://www.digikey.com/product-detail/en/harwin-inc/S1911-46R/952-1740-1-ND/3131071 >> >> If the assembly house doesn't like the 1206 resistor, it wouldn't be the >> worst thing... > > Usually you can use a plain resistor ahead of a linear regulator, just pick whatever resistance won't cause problems anywhere.
I'm not sure what you are picturing. The original board was designed to work with an FPGA which was available in two versions, 3.3 volts everywhere or a 1.2 volt core. The (optional) 1.2 volt power converter chip was a buck switcher with an inductor on the output. I want to use a linear regulator instead so there won't be any new issues with EMI. Given this we may skirt by without redoing EMI testing. The only problem with this is the inductor footprint does not suit any resistor size without crowding nearby vias, reducing the clearance to around 7-8 mils. The assembly house may or may not have an issue with this, we'll see. I'm just looking for something that mechanically fits the pads and provides a short. 1206 is the closest fit I can find so far. A 1205 or better, 1104 would be perfect, but they don't exist. I thought I found a jumper that fits, but I was reading the specs wrong and it is too long. A piece of bus wire would be great, but I don't think you can pick and place them, lol. -- Rick C
On Thursday, June 30, 2016 at 11:26:43 AM UTC-4, rickman wrote:
> I want to use a linear regulator on a board where a buck switcher had > been designed in. No problem on the chip, there are thousands with a > compatible footprint for this TSOP-5 package. I need to replace the > inductor with a jumper, something that can be SMT assembled and of > course, inexpensive. > > The pads are spaced so a 1206 would reach but it is a bit wide with the > pads only 47 mils wide. More importantly there are vias about 15 mils > away which end up maybe 7 or 8 mils away with the wider part overhang. > I'm a little concerned with this spacing. An 0805 part would fit the > pads better, but doesn't quite reach the gap of 82 mils. > > I was searching for zero ohm resistors, but it occurred to me there may > be parts specifically designed as jumpers which might fit these pads > better. Anyone know of anything like this? Nearly any jumper of 110 to > 120 mils long and no more than 50 mils wide would do, better is 35 or 40 > mils wide. > > I did find this which is a bit more than resistors at $450 per reel. > > http://www.digikey.com/product-detail/en/harwin-inc/S1911-46R/952-1740-1-ND/3131071 > > If the assembly house doesn't like the 1206 resistor, it wouldn't be the > worst thing...
You could just use a super-low value inductor, same size. 0.47uH? Check for stability, of course, but I'd think most regulators wouldn't mind it. As far as they could see the load would still be massively capacitive at frequencies that matter. Cheers, James Arthur
rickman wrote:
> I want to use a linear regulator on a board where a buck switcher had > been designed in. No problem on the chip, there are thousands with a > compatible footprint for this TSOP-5 package. I need to replace the > inductor with a jumper, something that can be SMT assembled and of > course, inexpensive. > > The pads are spaced so a 1206 would reach but it is a bit wide with the > pads only 47 mils wide. More importantly there are vias about 15 mils > away which end up maybe 7 or 8 mils away with the wider part overhang. > I'm a little concerned with this spacing. An 0805 part would fit the > pads better, but doesn't quite reach the gap of 82 mils. > > I was searching for zero ohm resistors, but it occurred to me there may > be parts specifically designed as jumpers which might fit these pads > better. Anyone know of anything like this? Nearly any jumper of 110 to > 120 mils long and no more than 50 mils wide would do, better is 35 or 40 > mils wide. > > I did find this which is a bit more than resistors at $450 per reel. > > http://www.digikey.com/product-detail/en/harwin-inc/S1911-46R/952-1740-1-ND/3131071 > > > If the assembly house doesn't like the 1206 resistor, it wouldn't be the > worst thing... >
THINK! Use an 1206 0-ohm resistor and place it in its side; "problem" solved.
On 7/1/2016 1:14 AM, Robert Baer wrote:
> rickman wrote: >> I want to use a linear regulator on a board where a buck switcher had >> been designed in. No problem on the chip, there are thousands with a >> compatible footprint for this TSOP-5 package. I need to replace the >> inductor with a jumper, something that can be SMT assembled and of >> course, inexpensive. >> >> The pads are spaced so a 1206 would reach but it is a bit wide with the >> pads only 47 mils wide. More importantly there are vias about 15 mils >> away which end up maybe 7 or 8 mils away with the wider part overhang. >> I'm a little concerned with this spacing. An 0805 part would fit the >> pads better, but doesn't quite reach the gap of 82 mils. >> >> I was searching for zero ohm resistors, but it occurred to me there may >> be parts specifically designed as jumpers which might fit these pads >> better. Anyone know of anything like this? Nearly any jumper of 110 to >> 120 mils long and no more than 50 mils wide would do, better is 35 or 40 >> mils wide. >> >> I did find this which is a bit more than resistors at $450 per reel. >> >> http://www.digikey.com/product-detail/en/harwin-inc/S1911-46R/952-1740-1-ND/3131071 >> >> >> >> If the assembly house doesn't like the 1206 resistor, it wouldn't be the >> worst thing... >> > THINK! Use an 1206 0-ohm resistor and place it in its side; "problem" > solved.
THINK! An assembly house can't auto pick and place that as the vacuum nozzle can't pick it up by its side! Problem totally not solved... -- Rick C
On Thu, 30 Jun 2016 21:14:16 -0800, Robert Baer
<robertbaer@localnet.com> Gave us:

>rickman wrote: >> I want to use a linear regulator on a board where a buck switcher had >> been designed in. No problem on the chip, there are thousands with a >> compatible footprint for this TSOP-5 package. I need to replace the >> inductor with a jumper, something that can be SMT assembled and of >> course, inexpensive. >> >> The pads are spaced so a 1206 would reach but it is a bit wide with the >> pads only 47 mils wide. More importantly there are vias about 15 mils >> away which end up maybe 7 or 8 mils away with the wider part overhang. >> I'm a little concerned with this spacing. An 0805 part would fit the >> pads better, but doesn't quite reach the gap of 82 mils. >> >> I was searching for zero ohm resistors, but it occurred to me there may >> be parts specifically designed as jumpers which might fit these pads >> better. Anyone know of anything like this? Nearly any jumper of 110 to >> 120 mils long and no more than 50 mils wide would do, better is 35 or 40 >> mils wide. >> >> I did find this which is a bit more than resistors at $450 per reel. >> >> http://www.digikey.com/product-detail/en/harwin-inc/S1911-46R/952-1740-1-ND/3131071 >> >> >> If the assembly house doesn't like the 1206 resistor, it wouldn't be the >> worst thing... >> > THINK! Use an 1206 0-ohm resistor and place it in its side; "problem" >solved. >
"Tombstoning" a part requires hand assembly operations. Automated assembly methods do not perform that way. THINK!